Dust collector



Oct. 21, 1941. H. P. BACON ETAL DUST COLLECTOR Filed Jan. 23, 1959 m m mww mm NMM m 3 em Z w the air.

' tween the size of the Patented Oct. 21, 1941 I UNITED 1 STATE s PATENT arms I DUST COLLECTOR Hollis P. Bacon,

A, Elben,leveland, Ohio, ern Blower Company, Cleveland,

ration of Ohio Cleveland Heights, and Iawrence assignors to North- Ohio, at corpo- Application January 23, 1939. Serial No. 252,212

1 Claim. (Cl. 183-83) This invention relates to an improved dust collector, and especially to an improved dust collector of the cyclonic type.

Cyclonic dust collectors'have heretofore been used with ajcylindricai expansion chamber and a tubular baffle member extending axially thereof, with a frustro-conical'dust collecting portion at the bottom of the cylindrical portion. Such collectors, however, have produced-a relativelylow operating-eificiency; that is the ratio of dustremoved to that supplied. For example, the average emciency of removing sawdust has been about 70%; that for grinding dust has been between 62 and 65%, and that. for removing limestone dust has been about 52%. Moreover, the cyclonic dust collectors heretofore used could not remove material measuring under 7% mi-' crons to any appreciable extent. Such material therefore has been carried through the collector with the exhausted air and deposited on the ground surrounding the plant.

that can be removed in a collector of the cyclonic type heretofore set forth.

A further object is to make arrangements for increasing the operating efliciency without materially increasing the cost of construction of the collector.

Other objects and advantages of the presentinvention will become more apparent from the This, therefore, is

the general object of the present invention.

invention is to corre the amount of air to be handled and its desired velocity within the baflle. The specific relationship which we have found to produce satisfactory results will hereinafter be set ,forth in the following description.

Inthe'drawing, Fig. 1 is a vertical axial section of my improved dust collector; Fig. 2 is a hori-- zontal section of the dust collector as indicated by the lines 2-4 on Fig. 1; Fig. 3 is a vertical as indicated by the.

section of the dust collector line 33 on Fig. 1. f

We have shown our invention in connection with a cyclonic dust collector which has a casing 3! which forms a cylindrical main expansion chamber I 0, within which a tubular baflie II is concentrical y disposed. The upper end of the expansion chamber i0 is closed by a plate [2 while the lower end opens into a frusto-conical V dust,'colle'cting portion' IS, the bottom of which dust is conveyed by a screw conveyor (not terminates in a conduit l4 through which the shown). The casing 3| is provided with a circulair inlet opening. 32-, in other words an inlet opening which is defined by the intersection of a cylinder with the casing 3| The supply conduit for bringing the dust laden air to the 001- lector is indicated as a cylindrical pipe l5 shown as leading from a stack 2| and connected to the chamber It by a frusto-conical connection I],

which forms an expansion-chamber 30, and-a cylindrical connection member. [8.

The dust laden air is drawn from a blower, generally indicated at '20, the outlet of which communicates with the stack 2| which is in communication as indicated at 22 with the inlet tube l5 of. the dust collector. The air passes through the dust collector, rising upwvardfollowing description which refers to a preferred embodiment of the invention as illustrated in the 4 accompanying drawing. The'novel features of the invention will be summarized in t he claim,

The foregoing objects are accomplished by utilizing an incoming air velocity materialy higher than thatcustomarilyused and by passing the air through an expansion chamber before it enters the main chamber, and by maintaining a definite relationship between the velocities of the air at the intake'point, at the end of the first expansion point, and in the central baflie which comprises the discharge conduit. Moreover, wemaintain a definite relationship beconduit at the end of the first expansion and the radial distance between the main expansion member and the central baille. The size of the baflle is determined from 1y through the tube H passing into a hood 23 which is secured to the top of'the' tube II and is of a gradual decreasing cross-sectional area.

This hood is connected by an outlet tube 24 with the stack 21 at a point some distance above the connection '22 between the stack and the'inlet tube IS. A suitabe damper 25 is positioned in the stack 2| so that the dust laden air passing upwardly in the stack must pass through the dust collector before continuing its progressthrough the stack. The damper, however, may be turned to'a vertical positi on so as to by-pass the dustcollector when desired.-

As heretofore mentioned, the arrangement is such that the dust laden air: enters the expani sion chamber immediately before its entrance to the'main expansion chamber l0 of the dust collector. As shown in the drawing, the inlet tube I5 is 'cylindrically shaped and is coaxial with the frusto-conical tube H which is arranged so that its'cross-se'ctional area gradually increases as it approaches the dust collector III. This frustoconicaltube provides the pre-expansion chamber its source by,

30 and permits the dust laden air to expand gradually as it approaches the'main expansion chamber which includes that area between the inner surface of the casing 31 and the external surface of the tube I. It is to be noted-that the inlet'tube I 5, the pre-expansion chamber 30 or frusto-conical tube l1 and the connection It are so arranged that the passageway therethrough is tangential to the main expansion chamber M.

The features above mentioned permit the dust laden air to enter the main expansion chamber at a much'higher velocity than possible in the past, and when combined with the-use of a high velocity of moving air, causes smallerand more dust particles to be removed from the dust laden air, thereby materially increasing the efllciency of the dust collector.

We have discovered that the emciency of operation, as measured by the percentage of dust removed, is dependent upon the relationship between the velocity of the air at various points in its path of travel and the sizes of the collector parts. We have also discovered that for best results, a. velocity of 3800-ft. per minutein the supply conduit i5 is desirable for carrying the maximum quantity of dust with the air. Such velocity is materially higher than that customarilyused heretofore; the averageprevious velocity being of the order of 2200-ft. per minute in the supply conduit. For best results then, we have also found that the size of the pre-expansion chamber should be sufflcient to reduce the yelocity of the air to 3200-ft. per minute and that the velocity in the baffle or conduit II should be '700-ft'. perminute. We have also discovered that equal to the diameter of the pipe l8. While we have stated that the preferred velocity of air is 3800-ft. per minute at the source of supply. we do not wish to be limited specifically to that amount, because it may vary with the specific gravity of material that is to be handled. We believe that the velocity may vary between 3000 and 5000,1t.

per minute, the higher velocity being required for the heavy materials. In any event, the supply velocity should bear a relationship to that at the end of the first or pre-expansion chamber, and to that in the'central tubular battle in. the proportion'of 3800 to 3200 to TOO-ft. per minute respectively. Thus, where-the supply velocity is 5000 ft. per minute, the corresponding velocity at the .end of the first-expansion would be approximately 4200-ft. per minute, and the correspending velocity in the tubular baiile would be the distance between the outer-surface of the baflle II and the inner surface of the. chamber l0 should be substantially equal to the diameter of the intake conduit at the point where the velocity "of the air is 3200-ft. per minute; or in other words, at the largest end of the expansion chamber 30. This arrangement causes the air to flow spirally within-the main chamber without interferen e between the turns as indicated by the dot and dash lines in Fig. l.' This minimizes the internal friction and aids materially in the re-' the pipe I5 and then the expansion necessary to reduce the velocity to 3200-feet per minute in the pipe l8 determines the diameter of the pipe I8. The space between the conduits l5 and I8 comprises a pre-expansion chamber which is preferablyin the form. of a frustro-conical section. Velocity in feet per minute as used herein refers to lineal speed, that is the lineal distance in feet the dust laden air would travel in one minute regardless of the volume of air involved.

The desired velocity of '700-ft. per minute in the tubular bafile ll determines the diameter of it and from that diameter, the size of the main chamber I0 is determined by making the distance between the outer surface of the conduit II and the inner surface of the chamber l0 substantially the old and new methods.

inlet pipe andithe 4 approximately 900-ft. per minute. Again, where the supply velocity is about 3000 ft. per minute, the corresponding velocity at the end of the first expansion would be approximately 2500-ft. per

minute while that in the tubular baiile would be about 550-ft. per minute.

A comparative test using cement dust weighing 73-lbs. when loosely packed wherein 99% of the material would pass through a 325-mesh screen,

and wherein 38% of the total material was under 7 microns showed, under the old method of collection, substantially no collection of material under 7 microns, and an average collection emciency of 48%, whereas under our new method, the collection of material under 7 /2 microns was about 15% while the average efliciency was about Other tests made on different materials likewise showed a material increase in eiliciency between For example, on saw This is an increase in eificiency of about dust the average efllciency= under the old method was about 70%, but under the new method was about 96%. On grinding dust the emciency under the old method was about 62 to 65% and under the new between 92 and 95%. On limestone the tests showed an average collection efllciency under the old method of about 52% and under the new method of about 89%.

We claim:

A cyclonic dust collector having a main cylindrical expansion chamber and a cylindrical bailie extending coaxially thereof and positioned therein and extending downwardly from the top of the main chamber, and having a funnel-shaped vortex chamberv below the main expansion chamber, an air admission conduit connected to the main expansion chamber, said conduit having one side thereof extending tangentially to the exterior wall of the main expansion chamber, said air admission conduit having means for expandingthe air in advance of main expansion chamber, the first expansion means comprising a tapered member having a base, the horizontal cross-sectional dimension of which is'substantially equal to the radial distance between the outer surface of the baille and the inner surface of the main expansion chamber, and the bottom of the air admission conduit being spaced above the bottom of the bailie by an amount at least equal to the vertical cross-sec tional dimension of the base of the air admission conduit.

HOLLIS P. BACON.

LAWRENCE A. EIBEN.

its admission into the 

